Pioneer 11, a robotic spacecraft launched 50 years ago on April 5, 1973, was one of the first spacecraft to explore interstellar space and the first to reach Saturn. Pioneer 11 is still traveling and its next destination is one of the stars in the Aquila (Eagle) constellation, with an estimated time of arrival of 4 million years. Pioneer 11 achieved fame by conducting fly-bys of Jupiter and Saturn, sending back volumes of data about the distant planets and even discovering a couple more moons at the latter planet, as well as a new ring. Pioneer 11 was part of NASA’s unprecedented plans to explore the outer solar system, with a total budget of $350 million. Pioneer 11 and its twin spacecraft, Pioneer 10, facilitated complex missions to Uranus and Neptune by their Voyager successors to the edge of the solar system and beyond. Pioneer 11 carried a gold-plated aluminum plaque with greetings from Earth and identical gold-plated LP records holding two hours of Earth sounds, including salutes in 58 languages. After 50 years, Pioneer 11 is an estimated 10.2 billion miles from Earth, and its last data transmission was in late 1995. Pioneer 11’s ultimate path was decided by celestial mechanics to ensure it was on track to Jupiter and Saturn.
